An Israeli firm has accused Microsoft of using its technologies in key components of Windows Update, court documents show.

BackWeb Technologies Ltd. filed its lawsuit in San Francisco federal court on Friday, charging that Microsoft's Background Intelligent Transfer Service (BITS) infringes several of its patents. BITS, which debuted in 2001 in Windows XP and is baked into Windows Vista, Server 2003 and Server 2008, is a file transfer service that can throttle back download speeds so they don't affect other network chores. Because of its duties -- it also resumes interrupted downloads -- BITS is a core part of Windows Update, Windows Server Update Services, and other Microsoft update and patching products.

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In 2007, as part of Vista, Microsoft updated BITS to Version 3.0, adding peer-to-peer characteristics that let PCs on the same subnet transfer files to and from peers.

BackWeb's lawsuit alleges that Microsoft's BITS infringes four of its patents, the oldest granted by the U.S. Patent and Trademark Office in 1999, the newest in 2003.

"[The patents cover] unique and novel methods and processes for transmitting digital information in background mode over a communications link between a computer network and a local computer and throttling the transfer speed to create minimal interference with other processes communicating over a communications link," BackWeb's filing read.

That fourth patent, issued to BackWeb in 2002, deals with what the company said is a technology "for distributing data packages across a hybrid peer-to-peer network."

BackWeb asked the court to force Microsoft to stop infringing its patents, and to triple any damages because Microsoft allegedly knew it was abusing BackWeb's patents when it created BITS.

Microsoft declined comment Tuesday. "We have not yet been served," said company spokesman David Bowermaster, "so it would be premature to comment."

BackWeb was not immediately able to provide answers to several questions, including whether the company had been in licensing talks with Microsoft prior to filing the lawsuit, and if so, why they might have broken off.

Coincidentally, Microsoft recently settled another patent-infringement case with PalTalk Holdings, a New York company that had demanded $90 million in royalties over Microsoft's Xbox Live online gaming service. Financial details of the settlement were not disclosed, but the deal two weeks ago brought a trial to a quick close.